Exhibit A – model of a Dell modular data centre boasting a PUE of 1.06 was on proud display at
Dell’s inaugural end user conference this past fall. PUE, and its companion DCiE, are
benchmarking standards designed by The Green Grid to calculate data centre energy efficiency which have come into broad use along with increasing concern over energy consumption and costs – and associated carbon outcomes. A measure of total power entering a data centre, divided by the energy used by IT equipment, PUE is expressed as a ratio, with overall efficiency improving as the quotient decreases towards 1. A PUE of 1.03, then, means that the Dell data centre comes reasonably close to perfect in terms of energy used by computing equipment within the facility.
A near perfect PUE? This result warranted further investigation, with evidence on the specific set of conditions that contributed to this result provided by David Hardy, modular data center marketing manager for Dell's data center solutions unit. In conversation with IT in Canada, Hardy cautioned that while a single PUE reading can be impressive, what is really important to the data centre operator is “average PUE over extended periods of time, based on real work loads.” PUE, he noted, also depends on where you measure it – Dell’s practise in the 1.03 case was to measure PUE at the power module used to feed distributed power to the IT module and the air handling unit. This measurement point means that there were site design and power system factors that could affect energy efficiencies in systems lying before the Dell module that data centre managers need also take into account which may affect the overall PUE of the whole facility. In other words, Dell’s near perfect PUE is a measurement of the power efficiency of components in the modular system only.
